In an image monitoring system or a medical image analysis system, a technique to track an object (a vehicle or an internal organ) in image sequence data is important. As a prior art, a tracking method in Japanese Patent Disclosure (Kokai) 2001-357403 is explained. First, a plurality of tracking points are initially set for a vehicle to be tracked. A movement of each tracking point is examined by using a template matching, and a weighted sum of a moving vector of each tracking point is calculated by using a residual of the matching. This weighted sum represents a moving vector of the vehicle. Next, a location of the vehicle is calculated from the moving vector of the vehicle. Last, by using Kalman filter for the location of the vehicle, a moving status (a location and a direction of movement) of the vehicle in actual space is estimated. In this way, the object is sequentially tracked. Hereinafter, this method is called a prior method.
In the case that the object is a rigid body, such as a vehicle, and the deformation is the same way as the prior method, a plurality of points in the object are tracked by using the template matching. In this case, the tracking result of the object is sufficiently reliable.
However, in the case that an deformable object, such as a person's facial image or a heart image in medical area is tracked, i.e., in the case that non-rigid body is the object to be tracked, each tracking point of the object may differently move by deformation of the object. Briefly, movement of the tracking points is not uniformed. In other words, a positional relation among a plurality of tracking points is changed by deformation of the object. Accordingly, in the prior method, by passage of time, it is often happened that a positional relation of a plurality of tracking point is inconsistent, and the tracking result of the object is not reliable.